1. Field of the Invention
This invention relates to apparatus for testing a chemical substance and more particularly, to an apparatus for testing the effect of antibiotics on a bacterial suspension.
2. Description of the Prior Art
The sensitivity of bacterial elements to antibiotics is usually ascertained by observing the reaction between a particular bacterial element and a plurality of chemical substances arranged in predetermined test zones or chambers provided within a testing apparatus. The testing apparatus usually is provided with a transparent covering so the effect of the various chemicals on the particular bacterial element may be easily observed and recorded.
In the prior art, it is common practice to individually apply or introduce the appropriate bacterial element into each of the reagent-containing test zones or chambers provided in a testing apparatus. As examples of one type of such prior art testing apparatus are U.S. Pat. Nos. 3,873,271 (Anderson), 3,829,223 (Hamel), and 3,759,666 (Hill). These mentioned patents utilize the centrifugal force of rotation of a testing apparatus to impel bacterial elements individually placed in a first chamber from that chamber into a radially-outer test chamber. U.S. Pat. No. 3,826,717 (Gilbert), and U.S. Pat. No. 3,936,356 (Janin) describe a second such type of testing apparatus have a substantially planar test vessel again in which the bacterial element to be evaluated is individually placed within the test zones or chambers provided. U.S. Pat. No. 3,854,883 (Montagnon), and U.S. Pat. No. 3,876,377 (Cinqualbre) also disclose testing apparatus having single or plural test zones requiring individual introduction of bacterial elements thereinto.
U.S. Pat. Nos. 3,373,719 (Avakian), 3,476,515 (Johnson), 3,649,464 (Freeman), 3,713,985 (Astle), and 3,728,228 (Duranty) disclose testing apparatus having individual test zones arranged in side-by-side relationship. U.S. Pat. Nos. 3,832,532 and 3,895,661 (both to Praglin) describe testing apparatus in which bacterial elements to be tested are first inserted in a reservoir provided at one end of the testing apparatus. The testing apparatus must then be rotated about a pivot point located at the reservoir end of the testing apparatus to dispose the bacterial elements into a plurality of interconnected distribution lobes. U.S. Pat. Nos. 3,925,166 (Blume) and 3,837,746 (Acker) require the presence of a differential pressure in order to draw the bacterial element to be tested into the appropriate test chambers.
Prior art testing apparatus also is known that requires provision to be made to prevent the dehydration of the bacterial elements after introduction to the testing apparatus. Such provisions usually include an enclosure or the like, disposed as a humidor, in order to maintain the desired humidity conditions for the test.
It is advantageous, therefore, to provide a testing apparatus for testing a substance that has a common reservoir into which the substance to be tested is placed, the reservoir supplying a plurality of individual test zones or chambers so that the time consuming individual introduction process may be avoided. It is also advantageous to avoid the requirement of applying a suction or pressure differential to draw the substance to be tested into the test zones. It is of further advantage to provide an apparatus which permits introduction of the bacterial element into each individual test zone or chamber expeditiously through the provision of a common reservoir and yet prevent intercommunication between the test zones or chambers which may vitiate the test. It is of still further advantage to provide a testing apparatus which does not require centrifugal force to draw the bacterial elements into the test zones, and, therefore, does not require expensive equipment, such as a centrifuge, in order to perform a test on a given bacterial element. It would be of even further advantage to provide a testing apparatus of a construction such that even inadvertent spillage of bacterial elements from the individual test zones or chambers back again into the common reservoir would not compromise the test efficiency. Also advantageous is a testing apparatus which allows access to the individual test zones or chambers without disturbing the other test zones. It is also advantageous to provide a testing apparatus which maintains a predetermined humidity condition within the test zones or chambers, to avoid dehydration of the bacterial elements, without the necessity of an associated humidor arrangement, or the like.